Comparative performance of isolated and fixed-base reinforced concrete structures

The earthquake transmits to the structure a large quantity of energy that causes damage to structures. The seismic isolation technique can absorb a large quantity of the seismic energy. The seismic isolation concept is a new technique in earthquake engineering, its principle is quite simple, and it consists to create a discontinuity between the foundation and the superstructure, so that seismic energy cannot be completely transmitted into the structure.Therefore, this article includes a numerical application of the nonlinear static method, the capacity spectrum method (CSM), on two types of structures, fixed base structure and isolated base structure. The CSM is one of the methods used for the evaluation of seismic performance. Its principle consists in superimposing a curve which represents the capacity of the structure originated from a non-linear static analysis (Pushover), with a curve representing the solicitation brought by the earthquake. The intersection of these two curves represents the point performance, which evaluates the maximum displacement of the structure in the plastic domain

Elaboration et caractérisation de béton autoplaçant fibré avec ajout de poudre de marbre

179 p. : ill. ; 30 cmA ce jour, peu d'applications pratiques ont été réalisées qui exploitent pleinement les propriétés rhéologiques et mécaniques des bétons autoplaçants fibrés. Les utilisations les plus courantes s'adressent plutôt à la durabilité des structures. Cela est en partie dû à un manque de connaissances exhaustives sur le comportement à la rupture des éléments en BAPF, ce qui est souligné par le peu de documents réglementaires spécifiques à ce sujet. Le coût des BAPF et la nécessité d'une mise en œuvre soignée sont d'autres facteurs qui limitent pour le moment sa diffusion. Le sujet de recherche s'articule autour de la formulation et la caractérisation des bétons autoplaçants BAP avec et sans fibres confectionnés à partir d'une gamme de constituants disponibles localement (contexte algérien) et qui répondent à un certain nombre d'exigences. L'Algérie dispose d'immenses quantités de sous-produits industriels, tels que la poudre de marbre, dont sa valorisation dans les matériaux cimentaires pourrait constituer une alternative écologique et économique intéressante, permettant d'élargir le champ d'emploi de la poudre de marbre et l'élimination de décharges encombrantes. Le but de ce travail en premier lieu est l'exploitation de la poudre de marbre dans les BAP comme ajout et sa substitution partielle au ciment à différents dosages et surface spécifique. À cet effet, une étude comparative a été menée sur un béton de référence avec addition calcaire. Les résultats obtenus montrent que malgré les avantages techniques, économiques et écologiques rapportés par l'utilisation des ciments en substitution partielle avec poudre de marbre, ces derniers restent associés à des inconvénients. Il est donc nécessaire de savoir si des ciments à plusieurs composants (binaire, ternaire et quaternaire) ont des effets synergiques de façon à ce que leurs ingrédients arrivent à compenser leurs faiblesses mutuelles. Pour améliorer quelques propriétés mécaniques des bétons autoplaçant (résistance à traction, ductilité...), des fibres sont incorporées. Une première étude, contribue à la compréhension des effets d'optimisation du dosage en fibres métalliques en fonction des longueurs. La deuxième action porte sur La combinaison des fibres qui est souvent appelée hybridation. Des mélanges mixtes ou hybrides ont été formulés avec des fibres métalliques, de polypropylène et de verre de différentes longueurs et dosage. Les résultats trouvés confirment que l'utilisation de deux types de fibres ou plus avec des dimensions différentes et des dosages appropriés peut potentiellement améliorer les propriétés intrinsèques du béton autoplaçan

The effect of hybrid steel fiber on the properties of fresh and hardened self-compacting concrete

Self-compacting concrete (SCC) offers several economical and technical benefits, the use of steel fibers extends its possibilities. This study was performed to compare the properties of SCC and fiber reinforced self-compacting concrete (FRSCC) with high volume of mineral addition. Six mixtures were elaborated in this study. The content of the cementitious materials and the water/cementitious materials ratio were kept constant, 500 kg/m3 and 0.34 respectively.The self-compacting mixtures have been prepared with a cement replacement of 30% by weight of marble powder. Two different types of steel fibers were used in combination with different lengths (50 mm and 30 mm), keeping the total fiber content constant at 60 kg/m3. Slump flow time and diameter, sieve stability, and L-Box were performed to assess the fresh properties of the SCC and FRSCC. Compressive strength, splitting tensile strength, flexural strength and ultrasonic pulse velocity were determined for the hardened properties. A marginal improvement in the ultimate strength was observed. The addition of steel fiber enhanced the ductility significantly and the results indicated that high-volume of marble powder can be used to produce FRSCC, even though there is some decrease in the compressive strength because of the fiber geometry which affects the properties of SCC mixtures not only in the fresh state but also in the hardened state

The effect of hybrid steel fiber on the properties of fresh and hardened self-compacting concrete

Self-compacting concrete (SCC) offers several economical and technical benefits, the use of steel fibers extends its possibilities. This study was performed to compare the properties of SCC and fiber reinforced self-compacting concrete (FRSCC) with high volume of mineral addition. Six mixtures were elaborated in this study. The content of the cementitious materials and the water/cementitious materials ratio were kept constant, 500 kg/m3 and 0.34 respectively. The self-compacting mixtures have been prepared with a cement replacement of 30% by weight of marble powder. Two different types of steel fibers were used in combination with different lengths (50 mm and 30 mm), keeping the total fiber content constant at 60 kg/m3. Slump flow time and diameter, sieve stability, and L-Box were performed to assess the fresh properties of the SCC and FRSCC. Compressive strength, splitting tensile strength, flexural strength and ultrasonic pulse velocity were determined for the hardened properties. A marginal improvement in the ultimate strength was observed. The addition of steel fiber enhanced the ductility significantly and the results indicated that high-volume of marble powder can be used to produce FRSCC, even though there is some decrease in the compressive strength because of the fiber geometry which affects the properties of SCC mixtures not only in the fresh state but also in the hardened state

Fresh and hardened properties of self-compacting concrete with different mineral additions and fibers

In this work, several reinforced self-compacting concretes were prepared by using three types of fibers made of steel, polypropylene and glass, and three different types of mineral additions (marble powder, metakaolin and limestone powder). The water to cement ratio was kept constant at 0.34 and fibers were used in combination, keeping the total fiber content constant at 60 kg/m3. Slump flow diameter, L-Box, stability and air content were performed to assess the fresh properties of the concrete. Compressive strength, flexural strength, splitting tensile strength and ultrasonic pulse velocity of the concrete were determined for the hardened properties.Noteworthy performances were generally obtained, particularly in hardened properties for the self-compacting concretes prepared with steel fibers in association with polypropylene fiber and marble powder as mineral addition

Fresh and hardened properties of self-compacting concrete with different mineral additions and fibers

In this work, several reinforced self-compacting concretes were prepared by using three types of fibers made of steel, polypropylene and glass, and three different types of mineral additions (marble powder, metakaolin and limestone powder). The water to cement ratio was kept constant at 0.34 and fibers were used in combination, keeping the total fiber content constant at 60 kg/m3. Slump flow diameter, L-Box, stability and air content were performed to assess the fresh properties of the concrete. Compressive strength, flexural strength, splitting tensile strength and ultrasonic pulse velocity of the concrete were determined for the hardened properties. Noteworthy performances were generally obtained, particularly in hardened properties for the self-compacting concretes prepared with steel fibers in association with polypropylene fiber and marble powder as mineral addition

The effect of hybrid steel fiber on the properties of fresh and hardened self-compacting concrete

Self-compacting concrete (SCC) offers several economical and technical benefits, the use of steel fibers extends its possibilities. This study was performed to compare the properties of SCC and fiber reinforced self-compacting concrete (FRSCC) with high volume of mineral addition. Six mixtures were elaborated in this study. The content of the cementitious materials and the water/cementitious materials ratio were kept constant, 500 kg/m3 and 0.34 respectively. The self-compacting mixtures have been prepared with a cement replacement of 30% by weight of marble powder. Two different types of steel fibers were used in combination with different lengths (50 mm and 30 mm), keeping the total fiber content constant at 60 kg/m3. Slump flow time and diameter, sieve stability, and L-Box were performed to assess the fresh properties of the SCC and FRSCC. Compressive strength, splitting tensile strength, flexural strength and ultrasonic pulse velocity were determined for the hardened properties. A marginal improvement in the ultimate strength was observed. The addition of steel fiber enhanced the ductility significantly and the results indicated that high-volume of marble powder can be used to produce FRSCC, even though there is some decrease in the compressive strength because of the fiber geometry which affects the properties of SCC mixtures not only in the fresh state but also in the hardened state

Fresh and hardened properties of self-compacting concrete with different mineral additions and fibers

In this work, several reinforced self-compacting concretes were prepared by using three types of fibers made of steel, polypropylene and glass, and three different types of mineral additions (marble powder, metakaolin and limestone powder). The water to cement ratio was kept constant at 0.34 and fibers were used in combination, keeping the total fiber content constant at 60 kg/m3. Slump flow diameter, L-Box, stability and air content were performed to assess the fresh properties of the concrete. Compressive strength, flexural strength, splitting tensile strength and ultrasonic pulse velocity of the concrete were determined for the hardened properties. Noteworthy performances were generally obtained, particularly in hardened properties for the self-compacting concretes prepared with steel fibers in association with polypropylene fiber and marble powder as mineral addition

Contribution of the Blast Furnace Slag on the Behavior of HPC in a Hydrochloric Environment

Most mechanical properties and durability of cementitious materials are related to the performance of the hydrated cement that coats the granular skeleton. However, different mineral additions are currently used in concrete. They are used as addition or substitution to cement. The use of these supplementary cementitious materials provides to concrete a denser matrix that will be more resistant to aggressive environments such as sulphates, chlorides and other aggressive agents. In mixtures containing finely ground of slag, 15% of cement by weight was replaced with finely ground of slag of El-Hadjar (Algeria). The main objective of this study is to investigate the effect of curing in the hydrochloric environment by subjugating its granular effect on the performance of concrete. Density, compressive strength, concrete surface, internal microstructure and ultrasonic pulse velocity were investigated in this research. The damage mechanisms of concrete have been related to the development of the microstructure of the material. The degradations were observed using a scanning electron microscope (SEM) and quantified by x-ray diffraction (XRD). The microstructural study concerns both the surface layer and the internal structure of the samples. The results have shown that slag of El-Hadjar present a pozzolanic activity and hence it affects favorably the microstructure of the paste which becomes denser and less permeable

Etude du comportement mécanique en statique des matériaux composites stratifiés en flexion 3 points

Au cours de ces dernières années, l'industrie de la transformation des materiaux composites à bénificié d'une croissance rapide et réguliére, soutenue en particulier par la diversité des applications. ce travail à pour but d'étudier le comportement mécanique en flexion 3 points en statique de differents stratifies croisés constitués de fibres de verre, de kevlar et hybride verre-kevlar et de la résine epoxyde, l'etude porte dans un premier temps sur l'etude des effets de la séquence d'empilement, les épaisseurs des couches à 90° sur le comportement mécanique des stratifiés. en deuxieme terme l'application de la théorie classique des stratifiés à l'aide d'un programme élaboré pour but de révéler l'éffet de la séqquence d'empilement sur la distribution des champs de contraintes et de déformation éxprimé dans le repére global et l'orthotropi